High
C1 on Alpha CD24

Your boiler has detected a faulty internal sensor that monitors water temperature, causing the heating system to stop working for safety.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description

Primary return temperature sensor faulty (no heating); cold resistance approx. 12-14 kohms

Engineer required

This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Related fault codes

C2View →

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